Air is constantly being circulated in large cities as air conditioning and heating units intake city air and use it to heat and cool their offices and residential buildings. As urban populations expand, and as downtown buildings grow higher and higher, we often forget about the growing pollution within the downtown areas. And because these buildings are so close together, neighboring buildings are often forced to intake polluted air into their indoor air systems. To combat this issue, researchers from Concordia University have modeled scenarios and have figured out a way to solve a portion of circulating polluted air.

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By examining the pathway and amount of air pollution from a building to its neighbors downwind, researchers have come up with environmentally friendly building guidelines. This provides an update to the industry standards developed decades ago by the American Society of Heating, Refrigerating and Air-Conditioning Engineers — the international technical society that sets the rules for building ventilation.

Concordia researchers performed tests in the university's cutting-edge wind tunnel laboratory, a huge underground research facility which allows engineers to test the atmospheric dispersion of pollution and toxins in any given setting.

The study consisted of model configurations of buildings of varying sizes and shapes that were placed downwind of a building that was emitting toxins. Researchers then traced the path from polluter to polluted to see how much pollution buildings downwind were absorbing and where on those buildings that pollution was most concentrated.

Results show that air pollution that spreads from one building's exhaust stack to another's intake is affected by the height and spacing between buildings.

"We came up with three main guidelines for the placement of stack and intake in order to minimize the amount of air pollution that makes its way into downwind buildings," says Ted Stathopoulos, a professor in Concordia's Civil and Environmental Engineering department.

First, intake vents on buildings downwind of a polluter should be placed upwind of that building's stack, and closer to its more sheltered wall. Second, air intakes should not be placed on rooftop locations downwind of a low stack and the protected wall of the emitting building. Finally, by increasing the spacing between buildings, there will be a lower chance that pollutants will be re-ingested.

While the research will not reduce the amount of outdoor air pollution, it will be useful to architects and engineers when building new towers in order to ensure that polluted air is not re-circulated indoors.